A small base station (femtocell) which is called an HNB (Home Node B: home base station) and is assumed to be used, for example, at home has been studied. A femtocell is, for example, a micro/low-power indoor base station which covers an area within a radius of several meters to several tens of meters and is used for mobile communication services. A radio wave from a macrocell may not reach some locations such as indoors. The femtocell is an indoor base station for constructing a stable radio communication environment for an area in which the communication environment is poor and radio waves from macrocell stations do not reach. In the near future, it is expected that a large number of femtocells (HNBs) will be subordinate to a macrocell.
Since the femtocell (HNB) covers a small area, when a mobile station is moving, handover occurs more frequently in the femtocell than in the macrocell. Accordingly, a smooth handover control for the femtocell (HNB) is important. 3GPP (Third Generation Partnership Project) presents communication using a logical interface called Iurh for a handover between HNBs. Non Patent Literature 3 relating to the 3GPP defines Iurh Interface for performing communication by RNSAP (Radio Network Subsystem Application Part) Signalling between HNBs.
Non Patent Literature 1 to 9 disclose femtocells (HNBs) that perform communication via Iurh Interface. Patent Literature 1 presents a data transmission method for reducing data transmission paths for femtocells.